Fibromyalgia

Basics

Nonarticular, noninflammatory form of muscular and joint pain more common in females:
- Widespread pain from stimuli that do not normally cause pain (allodynia)
- >11 diffuse tender points
- Fatigue
- Sleep disturbance
- Muscle stiffness
- Difficulties with attention, memory
- Limited physical findings
Fibromyalgia is no longer a diagnosis of exclusion, may occur with other rheumatic diseases

Mechanism:
- Painful symptoms believed to result from greater activation of pronociceptive (pain-causing) system relative to antinociceptive (pain-dampening) system in brain and spinal cord
Abnormalities identified as possible mechanism:
- Increased substance P (facilitates pronociception)
- Decreased biogenic amines (NE, serotonin, dopamine), which facilitate antinociception
- Decreased gray matter in brain
- Genetics: 1/3 of patients with fibromyalgia have a close relative who is affected:
  - Candidate genes include 5-HT2A, serotonin transporter, D4 receptor, others
- Like many complex diseases, psychological factors play a role, with high incidence of psychiatric disorders
- In genetically predisposed individuals, likely starts as initial insult from age, trauma, illness, inflammation, etc.
- Hypothalamus–pituitary–adrenal axis stress-response dysfunction has been indicated to precede development of fibromyalgia

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